Oort Type Planet
Main article: Rocky Planets (Theoretical Models) An Oort type planet is the coldest theoretical model of an Outer Planet, orbiting far from its parent star. The name is not official and comes from the Oort Cloud. The same conditions apply for a Rogue planet, These planets, if they orbit a star, are so far that in practice we can consider they receive no heat. The Solar Constant is extremely low, below 0.00004, average temperatures are usually below 15 K. Relation with parent star Around majority of stars, the planet will receive small amounts of heat and light, with aSolar Constant of at maximum 0.00004, Around M - type stars (modeled for Barnard's Star): *Distance: over 2000 million km *Visual constant: lower then 0.00002 (for yellow wavelength) *Revolution period: over 105 years *Stellar gravity: below 0.001 *Hill sphere (assumed Earth's mass): over 33 million km Compared to the Solar System, this is beyond the orbit of Uranus. Around K - type stars (modeled after Epsilon Eridani): *Distance: over 21000 million km *Visual constant: below 0.00002 (for yellow wavelength) *Revolution period: over 1800 years *Stellar gravity: below 0.00001 *Hill sphere (assumed Earth's mass): over 220 million km Compared to the Solar System, this starts at the end of the Scattered Disk. Around G - type stars (modeled after Sol): *Distance: over 35 000 million km *Visual constant: below 0.00004 (equal with solar constant) *Revolution period: over 3 300 years *Stellar gravity: below 0.00004 *Hill sphere (assumed Earth's mass): over 330 million km No celestial body is known to orbit only within this region of space, but many objects (for example long term comets) are known to reach it. Around F - type stars (modeled after Procyon): *Distance: over 100 000 million km *Visual constant: below 0.00004 (for yellow wavelength) *Revolution period: over 14 000 years *Stellar gravity: below 0.000001 *Hill sphere (assumed Earth's mass): over 1000 million km This is further away then for our sun. Around A - type stars (modeled after Sirius): *Distance: over 170 000 million km *Visual constant: below 0.000005 (for yellow wavelength) *Revolution period: over 30 000 years *Stellar gravity: below 0.000001 *Hill sphere (assumed Earth's mass): over 1300 million km At this huge distance, a planet can have stable orbits for moons further away then the Jupiter is from the Sun. Around B - type stars (modeled after Rigel): *Distance: over 1 400 000 million km *Visual constant: over 0.000003 (for yellow wavelength) *Revolution period: over 200 000 years *Stellar gravity: below negligible *Hill sphere (assumed Earth's mass): over 2000 million km At this high distance, a planet will not have a stable orbit and might be kicked away by passing stars. Around O - type stars (modeled after R136a1): *Distance: over 100 000 000 million km *Visual constant: below 0.000003 (for yellow wavelength) *Revolution period: over 25 000 000 years *Stellar gravity: below negligible Hill sphere (assuming Earth's mass): over 100 000 million km Given the high distance, a planet might be outside the planet's Hill sphere. Around L - class brown dwarfs: *Distance: beyond 80 million km *Visual constant: below 1E-12 (for yellow wavelength) *Revolution period: over 2 years *Stellar gravity: below 0.15 Hill sphere (assuming Earth's mass): over 2 million km Gravity forces might look like those experienced by Ceres. Around T - class brown dwarfs: *Distance: over 50 million km *Visual constant: below 1E-17 (for yellow wavelength) *Revolution period: over 0.8 years *Stellar gravity: below 0.5 Hill sphere (assuming Earth's mass): over 1.2 The planet will be exposed to tidal forces similar to Mars. Around Y - class brown dwarfs: *Distance: over 7 million km *Visual constant: below 1E-32 (for yellow wavelength) *Revolution period: over 20 days *Stellar gravity: below 20 Hill sphere (assuming Earth's mass): over 200 000 km Tidal forces will be similar to Mercury. Physical and chemical composition These planets are not heated by their stars and they would behave like free-floating planets. Except for those orbiting brown dwarfs, no tidal forces would be felt. The only substance that might be in gaseous phase is helium. Everything else will be solid, including hydrogen. As we suspect the majority of them to be differentiated, on the surface we would find a thick layer (from a few km to hundreds of km) of solidified gasses. Maybe, they are placed in order to their boiling point: first carbon dioxide and ammonia, then methane, nitrogen and carbon monoxide. On top of all, there might be a layer of frozen hydrogen. Cosmic rays have an ionizing effect and can break longer molecules, forming tholins from methane. They also break water and ammonia molecules. All this produces hydrogen, which freezes and is not lost into space. Atmosphere The only gas that can be found around such a planet should be helium, since its boiling point is too low. Even the radiation from distant stars could be enough to support a helium atmosphere. Terraforming In order to terraform such a frigid world, we will need an artificial source of light and heat. There is no way a greenhouse gas could allow us to heat a planet, even at extremely high concentrations, up to water melting point. For more details, see Rogue planet and Artificial sun. Category:Terraformed models